Of all the fundamental forces, Gravity is the most fundamental to our experience on this planet. We’ve always known that what goes up must come down, though we never really knew why.

Aristotle believed that objects fell toward Earth because they wanted to move toward their “natural state”. Because Aristotle was wrong about everything.

Galileo proved that objects fall at the same rate regardless of how heavy they are, and that they fall at a constant acceleration of 9.8 meters per second squared.

Sir Isaac Newton was the first to grasp that gravity was an attractive force between objects with mass and was able to devise the equations around gravity that we still use today.

Then Einstein redefined our understanding of gravity as a curvature in space-time caused by objects with mass.

Now, a common misconception is that gravity doesn’t work in outer space because we always see astronauts in zero gravity.

And if you’re anything like me, you grew up seeing this and just thought that the further you get away from the earth’s surface, the less gravity affects you, and that’s why astronauts get to float around all cool up there like that.

But that’s not how it works. That’s not how any of this works.

The reason these astronauts are floating is because they’re in orbit around the planet. And orbit is basically a state of always falling.

So being on the ISS is basically like constantly being in an elevator that’s plummeting toward the ground.

Some people, myself included, originally mistook the higgs boson as the force carrier for gravity because when you look at the standard model of particle physics, the other three fundamental forces all have force carrier particles called bosons.

Specifically, photons, gluons, and w and z bosons.

But the higgs boson is the force carrier of the higgs mechanism, which is a totally different thing. So I was wrong. I know, go figure.

But because all the other forces have force carrier particles, it was assumed that gravity would as well, which scientists called the graviton.

The graviton, if it exists, would be massless, because it works over unlimited distances, and would be a spin-2 boson, also known as a tensor boson.

It’s been theorized a massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field would couple to the stress–energy tensor in the same way that gravitational interactions do.

Gravitons also pose a problem with a mathematical issue called renormalization.

These issues have spurred some researchers to look for answers outside of quantum field theory like in string theory.

Some have tried to merge the supersymmetry found in string theory with general relativity in what they call Supergravity.

In the 80’s a theory called Modified Newtonian Dynamics, or MOND was introduced which tries to explain the movement of stars in galaxies without the use of Dark Matter.

Later, in 2004, MOND got modified further to create tensor-vector-scalar gravity which relies on a relativistic lagrangian density that maintains the law of conservation of energy.

Another popular idea is Erik Verlinde’s entropic gravity, which argues that gravity is an emergent force that arises from entropy itself and not a fundamental force at all.

And who can forget the chameleon particle theory, which has a variable effective mass that is an increasing function of the ambient energy density, meaning the particle’s mass changes to cause different effects on the particles around it.

So strangely, the first force we were aware of has become the last to be fully understood. And the one that, if we do ever fully understand it, would unlock the secrets of the universe.

Today is Columbus Day in the United States, but with more people understanding the truth, that Christopher Columbus was a wretched human being, I try to find something positive to take out of the day.

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So back in January of 2016, Musk was speaking at SpaceX’s Hyperloop pod competition, when he said this: “It’s a really simple and obvious idea and I wish more people would do it: build more tunnels. Tunnels are great. It’s just a hole in the ground, it’s not that hard.

But if you have tunnels in cities you would massively alleviate congestion and you could have tunnels at all different levels – you could probably have 30 layers of tunnels and completely fix the congestion problem in high-density cities.

So I strongly recommend tunnels.” But it was something he just kinda said off the cuff and nobody but the most ardent Musk-watchers paid any attention to. He claims to have built a machine that can dig tunnels for transportation 500 to 1000% more efficiently than current boring machines. And his logic is that people in cities live and work in a 3D space, in vertical buildings that can house more people. But our city transportation is on a 2D plane, meaning all these vertically packed people are now crammed into a horizontal space. By creating a 3D transportation grid, we can alleviate the congestion and drive like civilized human beings.

And his logic is that people in cities live and work in a 3D space, in vertical buildings that can house more people. But our city transportation is on a 2D plane, meaning all these vertically packed people are now crammed into a horizontal space. By creating a 3D transportation grid, we can alleviate the congestion and drive like civilized human beings.

Now, there are a couple of criticisms of this plan, one is that this idea’s been around for over a hundred years, it’s called subways. And subways are great for densely packed urban areas like New York but for cities like LA, or Dallas for that matter, where things are spread far apart, not so much.

For example, it’s a 20 or 30 minute drive just to get to my closest light rail station, at that point, I might as well just drive the rest of the way. It’s just not practical. But underground highways under strategic high-traffic arteries could make a big difference. And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

Now, there are a couple of criticisms of this plan, one is that this idea’s been around for over a hundred years, it’s called subways. And subways are great for densely packed urban areas like New York but for cities like LA, or Dallas for that matter, where things are spread far apart, not so much.

For example, it’s a 20 or 30 minute drive just to get to my closest light rail station, at that point, I might as well just drive the rest of the way. It’s just not practical. But underground highways under strategic high-traffic arteries could make a big difference. And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work.

And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

But underground highways under strategic high-traffic arteries could make a big difference. And reducing the time cars are idling in traffic could cut down on pollution as well. The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put

The other criticism is that building tunnels is not nearly as easy as it sounds, even with a giant high-tech earthworm machine doing all the work. Obviously in urban areas there’s all kinds of things we’ve put under the ground in terms of sewers, gas lines, telecommunication lines and so forth.

But we at least know where those are, what we don’t know is other things like pockets of gas, unstable rocks, hidden fault lines, and so forth. But… I’m sure all those things will be addressed before any large-scale tunneling begins in LA., there’s a mountain of bureaucratic red tape to get past before that happens. Which should put completion around the Fall of… never. A side benefit of this tunnel machine would be for SpaceX’s future Mars

A side benefit of this tunnel machine would be for SpaceX’s future Mars colonies, since boring underground would be the best protection against cosmic rays. Now this is of course nowhere near Elon’s first foray into transportation, I mentioned earlier his hyper loop competition, well, he just hosted another competition in January. 27 teams entered designs, of those, 3 were picked to actually run, and of those, two won awards, one for design, and the other for speed, maxing out at 90 kilometers per hour, or 55 miles per hour.

That’s a far cry from the 900 miles per hour predicted for the hyper loop, but it’s early yet, and it’s only a one-mile stretch of track, so it’s probably not getting up to top speed.

Legendary oilman T. Boone Pickens called the US the Saudi Arabia of wind and when you see maps like this, you understand why.

As the Earth spins toward the west, it slides underneath the air in the atmosphere, giving it from our perspective a generally eastward direction.

That easterly wind sweeps over the rocky mountains and then rushes back down across the Great Plains, creating one of the largest wind corridors in the world.

And in the last 10 years, investments in commercial wind energy have boomed across the United States. Economies of scale have started to kick in, causing the price of wind turbines to drop.

They also cost little to maintain and operate and help create energy independence for smaller communities and provide a revenue source for local ranchers who lease out the land to the energy companies.

And they’re more space-efficient. On the ground they take up very little space and those ranchers can still use the land below them for agriculture.

Plus it’s a large growth sector for jobs and currently employs over 100,000 people, expected to rise up to 600,000 in the next 30 years.

And there’s a reason I saved saved solar for last. Because there’s something different about solar from all other forms of energy, clean or dirty.

Photovoltaic solar panels, or PV panels, have no moving parts.

Every other energy source creates electricity by using heat or steam or water or wind to turn a turbine. Solar literally just collects the energy coming out of the sun and repurposes it.

When asked if he was interested in fusion power as a source of energy, Elon Musk famously said that we already have a massive fusion reactor in the sky just feeding us energy every day. All we have to do is collect it.

Now there are some negatives to solar power, let’s just get that out of the way…

First the obvious one, there’s no sun at night, so solar power is intermittent. But intermittent more like tidal energy than wind energy because we know the sun will be coming up every day.

And even in cloudy weather, it is producing something.

They take up a lot of land, unlike wind farms mentioned earlier, if you have a solar farm, you can’t use that for other things.

But, you can also use existing infrastructure like buildings and transport corridors.

The big hangups come in the construction of the solar panels because there are some hazardous materials used that need to be properly disposed of at the end of the panel’s life span.

And some PV panels require rare Elements like those found in cadmium telluride (CdTe) or copper iridium gallium selenide (CIGS), which is all the more reason to recycle the panels properly.

Luckily, 96% of a solar panel can be recycled. Unfortunately, the recycling infrastructure for solar panels is pretty small, but expected to grow tremendously in the next 30 years.

But the one that gets the solar haters the most worked up is that producing solar panels does generate greenhouse gasses. Specifically nitrogen trifluoride and sulfur hexafluoride. And yes, that sucks.

But the argument that we should stick with something like coal because PV panels create greenhouse gasses is frankly absurd.

Because with the solar panels, it’s a one-shot deal and then you’re getting clean, free energy for the next 20 or 30 years, while coal is constantly pumping out greenhouse gasses that whole time.

This debate was laid to rest by Wilfried Van Sark of Utrecht University in the Netherlands. In a paper for the trade Nature Communications, he and his team calculated the amount of greenhouse gas emissions created by PV panel production all the way back to 1975 to see how long it would take before they made back their debt.

I didn’t even mention the other type of solar energy, concentrated solar thermal plants.

This week, paleontologists unveiled two remarkable new species of dainty gliding mammals that lived alongside dinosaurs nearly 160 million years ago.

While they are not the first mammalian gliders known from this time period, these specimens are unique because they have thin, furry membranes of skin attached to their front and back limbs that are clearly preserved in the rock.

“It is pretty obvious from looking at these fossils that they are gliders, due to the carbonized skin,” says study coauthor David Grossnickle, a Ph.D. candidate at the University of Chicago.

Named Maiopatagiumfurculiferum and Vilevolodon diplomyos, the two new species are offering clues to the ways various mammals have taken to the skies over evolutionary time scales.

“Gliding is one of the cutest and one of the most striking locomotor adaptations,” says study coauthor Zhe-Xi Luo, a paleontologist at the University of Chicago.

Both of the new gliders were found in the Liaoning region of China, which is famous for its stunning power of preservation.

The Jurassic-era lake sediments have yielded some of the finest fossils in the world, including scads of feathered dinosaurs and a myriad of early mammals with carbonized fur and soft tissue.

Even without the conspicuously preserved skin, the newfound animals’ well-preserved skeletal structures give away their gliding ability, the team reports in a pair of papers published this week in the journal Nature.

Grossnickle notes that the limb proportions of gliding mammals are quite different from those that simply climb trees or walk on the ground, and the two new specimens have limb proportions that are similar to modern gliding mammals.

Both fossils also have notable hands and feet, says Jin Meng, a paleontologist at the American Museum of Natural History who was not involved in either study.

“Our toes are very short because we have to walk on the ground,” he says. “These animals have much longer fingers, showing they have adaptations for grabbing on trees in the forest.”

Grossnickle adds that in both fossils, the hands and feet are very similar to those on modern bats.

“These things could be using all four limbs to roost like bats,” he says, and it’s even possible they spent time hanging upside-down from tree branches like modern flying lemurs.

The two new gliding mammals are among 10 similar species known to have lived in this area during the Jurassic, and that diversity means there were plenty of ecological niches for them to occupy.

Taken together, the traits of these fossil gliders seem to back up the hypothesis that different groups of mammals followed a similar evolutionary pattern of being land-based, then moving to tree-climbing, then to gliding.

Modern rodents and flying squirrels followed this pattern, along with Australian marsupials like sugar gliders.

“In the Jurassic forests, this group independently evolved this kind of locomotion like other living mammals that also glide,” says Meng. “Mammals started experimenting with different locomotion types very early on.”

Hydroelectric is the use of moving water to turn turbines that generate electricity, usually through the building of dams or pump stations on rivers.

And hydroelectricity is the king of renewable energy, making up 70% of the renewable energy produced around the world. And for good reason.

They’re kind-of the perfect energy source. It’s stable, base-load energy that’s flexible. If you need more electricity, just release more water into the turbines.

They’re cheap to run and maintain once they’re built and they’re 95% efficient at generating energy, compared to 33% for coal and 15% for solar.

And of course they create no pollutants, consume no fuel, and the water never stops flowing.

The Three Gorges Dam in China is actually the largest energy plant of any kind in the world and generates just under a hundred terawatt hours per year all by itself.

So, hydro is kinda perfect. The problem is, it’s location-specific.

If you don’t live by a large river, you’re not going to be able to use it. Luckily, most cities were built near rivers, but not all rivers are large and powerful enough to make enough difference to justify the cost of building them.

Which is also a problem. While they produce free energy for decades and even centuries after they’re built, hydroelectric dams are huge engineering projects that cost tons of money up front.

(By the way, the whole ‘expensive at first but then free for decades’ thing is a common theme amongst renewable energies)

They also create reservoirs and lakes that flood a lot of land whose landowners may not want to give up.

There are some concerns about the disruption of fish habitats, but… that’s not at the top if my list of concerns.

So each hydroelectric plant is a birds nest of legal and construction challenges to overcome but even so, the number of hydropower plants are expected to double by 2050.

Another base load energy source is geothermal energy.

Iceland and the Philippines are major producers of geothermal power, which can be used in huge commercial plants to power entire cities or just pump the heat directly into homes for heating.

It’s a consistent flow of energy so it never runs out, but the efficiency isn’t great. Only an average of 12% efficiency.

Which really just means it will take longer for the investment to build it to pay off because once it’s turned on, it’s just free energy basically. And the efficiency is getting better, with newer plants getting over 20%.https://www.geothermal-energy.org/pdf…

Even in Iceland, which is covered in hotspots and has a very progressive attitude toward clean energy, it only accounts for 30% of their energy production.

So it’s not likely to become a major source of energy worldwide

And as if all that wasn’t enough of a bummer, it also turns out that geothermal can produce greenhouse gasses.

Geologic hotspots churn up all kinds of stuff from inside the Earth, stuff like sulfur dioxide and silica emissions, and heavy metals like mercury, arsenic and boron.

These can get in the reservoirs and eventually the water supply.

Oh, and by the way, one of the methods they use to open up geothermal wells is hydraulic fracking. Yeah. That hydraulic fracking.

Let’s drill down and inject extremely high pressure water and other chemicals… Right over a volcano.

What could go wrong?

Earthquakes. That’s what.

Just like fracking for natural gas has caused earthquakes in Oklahoma…

(zoom in)Earthquakes. In Oklahoma.

A geothermal well that was drilled in Switzerland set off an earthquake that measured a 3.4 on the Richter scale.

(pained)Geothermal… Why do you hurt me so?

I used to think geothermal was really cool. Used to.

So am I wrong about this? Do you have experience using geothermal, or working in hydro plants? Are my numbers garbage? Let me know in the comments

The next video in this series will focus on biomass energy and harnessing the motion of the ocean to make power.

Isaac Arthur runs the YouTube channel Science and Futurism With Isaac Arthur, where he goes into incredibly deep dives on subjects like megastructures, future space colonies, aliens, and little things like farming black holes (like you do). Here we touch on a few of those topics and do a little shop talk about life as YouTubers.

This is the home of Answers With Joe, where I take questions and comments and deconstruct them to find the interestingness - the funny, unique, but universal truths that give you a new perspective on the world. Enter with an open mind. Leave with a blown one. New videos every Monday unless I screw up.